The Benchmark Assessment asked this:

An Upper Merion teacher was once quarantined during a medical procedure, because she was temporarily radioactive. Which explanation accounts for her radioactivity?

• A: She was exposed to intense gamma rays, which made her carbon-12 into radioactive carbon-14.
• B: She ingested radioactive medicine, and radioactive isotopes collected in her thyroid gland.
• C: She received high doses of x-rays, which remained in her body for an extended time.
• D: Wait! Every one of these answers could explain why she was radioactive!